NL2027741B1

NL2027741B1 - Heavy Duty Vehicle Stop Start System

Info

Publication number: NL2027741B1
Application number: NL2027741A
Authority: NL
Inventors: Van Reeven Vital; Theodorus Bernard Anna Kessels Johannes
Original assignee: Daf Trucks Nv
Priority date: 2021-03-11
Filing date: 2021-03-11
Publication date: 2022-09-27
Also published as: WO2022191708A1

Abstract

Truck driven by a powertrain, said powertrain comprising an internal combustion engine, a drive train, extending from the internal combustion engine and arranged for transmitting drive torque between the internal combustion engine and driven wheels of the truck, the drive train including an electric motor providing additional drive torque between the internal combustion engine and driven wheels of the truck, a stop-start controller, arranged for controlling the drive train to provide a requested launch torque of the powertrain based at least on measured signals from a throttle pedal of the truck, to launch the truck from standstill to motion while the internal combustion engine is switched off, wherein, while the truck is in standstill, the stop-start controller is arranged for performing i) in a first step, controlling the drive train to decouple from the internal combustion engine; and ii) in a second step, controlling the electric motor in the drive train to provide the requested additional drive torque, to launch the truck to motion without cranking the internal combustion engine regardless of a magnitude of the requested launch torque, wherein, when the truck is in motion, the stop-start controller is arranged for performing iii) in a third step, controlling the drive train to couple to the internal combustion engine; and iv) in a fourth step, controlling the electric motor to provide the additional drive torque to the internal combustion engine, in order to crank the internal combustion engine.

Description

P128085NL00 Title: Heavy Duty Vehicle Stop Start System Field of the invention

The invention relates to an engine stop-start system for a heavy duty vehicle.

Background of the invention Of particular interest are heavy duty vehicles, e.g. trucks typically larger than 6 tonnes gross vehicle weight, that are powered by an internal combustion engine.

Trucks in general are used to transport heavy loads over long distances.

Particularly in case of heavy duty long haulage applications so-called tractor semi- trailer combinations are used in which the tractor vehicle pulls and partly supports the payload that is packed onto the semi-trailer.

Engine stop-start, instead of running the internal combustion engine at idle speed, is an attractive feature to save fuel when a vehicle is standing still, e.g. when waiting for a traffic light, as known from passenger vehicles.

A disadvantage of switching off the internal combustion engine, is that time is needed to crank the engine when the driver wants to start driving again.

In passenger vehicles, however, the size of the internal combustion engine requires a relatively short cranking time, thereby limiting the effect on drivability.

Heavy duty vehicles typically have a combustion engine with a large displacement, e.g. more than 7 liters, compared to passenger vehicles.

Cranking an engine with a larger displacement requires more time, so the impact of having an engine stop-start system on drivability is more severe with trucks than with passenger cars.

In hybrid passenger vehicles, driven by an internal combustion engine and an electric motor, a stop-start system may not create engine re-start delay.

This can be attributed to hybrid passenger vehicles being principally designed to use the electric motor as the primary power source for fuel economy and emission reduction.

The internal combustion engine is used merely as a secondary power source, e.g. only in case the battery unit is depleted or when additional power is requested. Accordingly, hybrid passenger cars are equipped with an electric motor which is typically strong with respect to the internal combustion engine. For heavy duty vehicles having a gross vehicle weight larger than 6 tonnes, however, having a similar hybrid topology and corresponding power ratio would imply that an electric motor and accompanying battery unit(s) need to be considerably sized to serve as a primary power source. Implementing a stop-start system on a heavy duty vehicle by setting up a hybrid topology would therefore cause major changes to the conventional truck architecture. Especially when considering heavy duty long haulage applications, the properties of e.g. a diesel powered internal combustion engine with a displacement larger than 7 liters are not easily replaced by an electric power system, without increasing the overall vehicle dimensions and weight, and without raising the total investment costs and operating expenses for the transporter.

Alternatively, however, when conventional heavy duty vehicles are equipped with a stop-start system, there is also a risk that engine re-start takes a significant amount of time due to the large displacement engine, and that the driver experiences a substantial delay when driving off.

This delay can be unacceptable when driving in dense traffic, e.g. in situations when the driver is waiting at a junction or roundabout while priority must be given to other traffic. The driver needs to take into account the vehicle response, including the delay for engine re-start, when finding a proper moment to launch the vehicle between traffic. When the driver eventually decides to launch the vehicle but the response is too slow, this may lead to annoying, or even dangerous, situations for other drivers.

The present invention focuses on a heavy duty vehicle powered by an internal combustion engine, having an engine stop-start system without the drawbacks described.

Summary of the invention In summary, embodiments of the invention pertain to a truck driven by a powertrain. The powertrain comprises an internal combustion engine and a drive train, which extends from the internal combustion engine and which is arranged for transmitting drive torque between the internal combustion engine and driven wheels of the truck. The drive train includes an electric motor to provide additional drive torque between the internal combustion engine and the driven wheels of the truck. Furthermore, the drive train may optionally include a clutch and/or a transmission to couple and decouple the electric motor from the internal combustion engine and/or the driven wheels. The powertrain further comprises a stop-start controller, which is arranged for controlling the drive train to provide a requested launch torque of the powertrain, based at least on measured signals from a throttle pedal of the truck, to launch the truck from standstill to motion while the internal combustion engine is switched off.

While the truck is in standstill, the stop-start controller is arranged for performing in a first step, controlling the drive train to decouple from the internal combustion engine. By having the drive train decoupled from the internal combustion engine, the torque required to launch the truck from standstill to motion is reduced because the relatively large inertia and friction forces of moving parts of the high displacement internal combustion engine are decoupled from the driven wheels of the truck.

In a second step, while the truck is in standstill, the stop-start controller is arranged for controlling the electric motor in the drive train to provide the requested drive torque to the driven wheels, to launch the truck to motion without cranking the internal combustion engine regardless of a magnitude of the requested launch torque. By exclusively having the electric motor launch the truck regardless of the requested launch torque, a substantial delay when driving off, caused by the cranking time of the high displacement internal combustion engine, is avoided.

When the truck is in motion, the stop-start controller is arranged for performing in a third step, controlling the drive train to couple to the internal combustion engine, while, optionally, decoupling from the driven wheels. By having the drive train couple to the internal combustion engine when the truck is in motion, thus having a forward momentum, a suitable moment can be selected when coupling the internal combustion engine to the drive train will have an optimal effeet on drivability, fuel economy and power demand.

In a fourth step, when the truck is in motion the stop-start controller is arranged for controlling the electric motor to provide the additional drive torque to the internal combustion engine, in order to crank the internal combustion engine. By using the drive torque of the electric motor to crank the internal combustion engine when the truck is in motion, the internal combustion engine can quickly be cranked while maintaining a forward momentum of the truck.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be further elucidated in the figures: FIGs 1A-B show a truck driven by a powertrain according to a first embodiment; FIGs 2A-B show the truck according to a further embodiment; FIG 3 shows the truck according to another or further embodiment; FIG 4 illustrates another or further embodiment of the truck; FIG 5 illustrates yet another or further embodiment of the truck; FIG 6 provides an example of a functional architecture of a stop-start controller of the truck; FIG 7 provides an example of a sequence of steps performed by the stop- start controller, depicted in a table; FIG 8 provides another example of a launch sequence of the truck performed by the stop-start controller, depicted in a graph.

DETAILED DESCRIPTION Aspects of the invention relate to a truck driven by a powertrain, comprising an internal combustion engine providing drive torque, a drive train including an electric motor, and a stop-start controller. The latter is arranged for launching the truck from standstill to motion in a sequence of steps, including controlling the drive train to couple to the internal combustion engine and controlling the electric motor to provide additional drive torque to the driven wheels to launch the truck without cranking the internal combustion engine regardless of a magnitude of the requested launch torque. After the truck is brought to motion the stop-start controller is arranged for controlling the drive train and the electric motor to crank 5 the internal combustion engine. The benefit of the invention is that the fuel economy of the truck can be improved by being equipped with a stop-start system, without having a slow vehicle response when driving off due to cranking of the high displacement internal combustion engine. In some embodiments, the drive train comprises a clutch, arranged between the internal combustion engine and the electric motor for coupling and decoupling the drive train to and from the internal combustion engine, and wherein the stop- start controller is arranged for controlling the clutch correspondingly. The advantage of having a clutch arranged in the drive train between the internal combustion engine and the electric motor, is that it provides a device which can be controlled by the stop-start controller, by which the relatively large inertia and friction forces of moving parts of the internal combustion engine can be decoupled from the drive train to reduce the required launch torque, while the electric motor remains coupled to the driven wheels to launch the truck from standstill to motion.

Prior to controlling the drive train to couple to the internal combustion engine, the stop-start controller can be arranged for controlling the electric motor to reduce a rotational speed difference between the electric motor and the internal combustion engine. This can reduce the time required to couple the drive train to the internal combustion engine, and reduce the amount of energy that may otherwise be dissipated as waste heat during the coupling.

In some embodiments, the stop-start controller is arranged for using the electric motor as an electric generator to convert kinetic energy of the drive train into electric energy to reduce the rotational speed difference between the electric motor and the internal combustion engine. By converting kinetic energy into electric energy to reduce the rotational speed difference, and storing the electric energy in an electric energy buffer for later use, the total energy efficiency of the truck can be improved.

In other embodiments, the stop-start controller is arranged for controlling the electric motor to provide the additional drive torque in a negative direction,

opposite to a direction of the requested launch torque, to reduce the rotational speed difference between the electric motor and the internal combustion engine. In this way, the power of the electric motor can be used to reduce the rotational speed difference as quickly as possible, to minimize the time required to synchronize the rotational speed of the drive train and the internal combustion engine.

Alternatively or additionally, the drive train comprises a transmission, arranged between the electric motor and the driven wheels of the truck. The stop- start controller can be arranged for controlling the drive train to couple to the internal combustion engine and controlling the electric motor to crank the internal combustion engine during a gear shift, while drive torque is interrupted between the transmission and the driven wheels of the truck. The advantage of this arrangement is that the forward momentum of the truck is not influenced by the drive train being coupled to the internal combustion engine, and the internal combustion engine being cranked by the electric motor, because these steps are performed while the corresponding components are decoupled from the driven wheels of the truck.

In some embodiments, the stop-start controller is arranged for controlling the transmission to launch the truck from standstill to motion in a selected gear of the transmission, in dependence of a maximum additional drive torque that can be provided by the electric motor. In other or further embodiments, the stop-start controller is arranged for controlling the transmission to shift to a higher gear when the truck is in motion, in dependence of a maximum rotational speed of the electric motor. By taking into account the maximum additional drive torque and the maximum rotational speed of the electric motor, which can be different from the maximum torque and rotational speed of the internal combustion engine, the stop-start controller may decide to control the transmission with a specific gear shift strategy when the truck is driven by the electric motor, which can be different compared to when the truck is driven by the internal combustion engine. The specific gear shift strategy can for example be optimized for fuel efficiency, power, or drivability.

In yet further embodiments, after controlling the electric motor to crank the internal combustion engine, the stop-start controller can be arranged for synchronizing the internal combustion engine with the transmission during a gear shift, by using the electric motor as an electric generator to convert kinetic energy of the internal combustion engine into electric energy, to match a rotational speed of the internal combustion engine with a rotational speed of the transmission. This reduces the time required to synchronize the internal combustion engine with the transmission, thus allowing faster gear shifts, while recovering energy from the internal combustion engine, thereby improving the total energy efficiency of the truck.

In some embodiments, the stop-start controller is arranged for providing a power boost to the truck, after having controlled the electric motor to crank the internal combustion engine, by controlling the electric motor and the internal combustion engine to simultaneously drive the wheels of the truck in dependence of a trigger signal. The trigger signal can e.g. be provided by a kick down sensor in the throttle pedal. The power boost can be used to compensate for a limited acceleration of the truck when driven exclusively by the electric motor during the launch from standstill to motion.

In other or further embodiments, the truck further comprises a radar sensor for measuring a speed and distance of a predecessor vehicle, wherein the stop-start controller is arranged for controlling the drive train to couple to the internal combustion engine and controlling the electric motor to crank the internal combustion engine in dependence of measurements from the radar sensor. In this way, the truck can be controlled to automatically start driving and following the predecessor vehicle e.g. in a traffic jam situation, with optimal stop-start scheduling of the internal combustion engine for improved fuel economy and drivability.

Now turning to FIGs 1A-B, there is shown a first embodiment of a truck 1 driven by a powertrain, comprising an internal combustion engine 10, in particular a large displacement engine suitable for long haulage applications, e.g. a diesel engine, and a drive train 200. The drive train 200 extends from the internal combustion engine 10 and is arranged for transmitting drive torque between the internal combustion engine 10 and driven wheels 7, e.g. the rear wheels of the truck 1. The drive train 200 includes an electric motor 210 that provides additional drive torque

Td between the internal combustion engine 10 and the driven wheels 7 of the truck

1.

Optionally, as shown in FIG 1A and 1B and as is common for conventional trucks, the drive train 200 can comprise a transmission 230 between the electric motor 210 and the driven wheels 7, though this is not an essential feature of the present invention.

Compared to the internal combustion engine 10, the electric motor 210 preferably has a relatively low maximum power, e.g. the maximum power of the electric motor is less than 40% of the maximum power of the internal combustion engine, or between 20% and 40% of the maximum power of the internal combustion engine.

The powertrain further comprises a stop-start controller 500, which is arranged for controlling the drive train 200 to provide a requested launch torque of the powertrain based at least on measured signals from a throttle pedal 80 of the truck 1, to launch the truck 1 from standstill to motion while the internal combustion engine 10 is switched off.

Measured signals from the throttle pedal 80 can e.g. be representative of an absolute or relative throttle position, a first or second order change in throttle position, or a throttle pressing force exerted by the driver on the throttle pedal 80.

The stop-start controller 500 is arranged for performing a sequence of steps based on the status of the truck 1. While the truck 1 is in standstill, as represented by FIG 1A, the stop-start controller 500 is arranged in a first step for controlling the drive train 200 to decouple from the internal combustion engine 10, such that no drive torque is transmitted between the internal combustion engine 10 and the driven wheels 7 of the truck 1.

For example, to interrupt the drive torque between the internal combustion engine 10 and the driven wheels 7 of the truck 1, the drive train 200 may comprise a coupling means 205 such as a clutch or transmission, arranged between the internal combustion engine 10 and the electric motor 210, and which can be controlled by the stop-start controller 500. In FIG 1A, the coupling means is shown in an open, decoupled position.

In a second step, the stop-start controller 500 is arranged for controlling the electric motor 210 in the drive train 200 to provide the additional drive torque Td to the driven wheels 7 to launch the truck 1 to motion without cranking the internal combustion engine 10, regardless of a magnitude of the requested launch torque.

For example, FIG 1A shows that the additional drive torque Td is directly provided by the electric motor 210 onto the drive train 200 to drive the driven wheels 7 of the truck 1, e.g. by having the rotor of the electric motor 210 coaxially aligned with a central drive shaft of the drive train 200. Alternatively, the additional drive torque Td can be provided onto the drive train 200 by means of a mechanical transmission, e.g. a gear, belt or chain transmission, so that the electric motor 210 can be placed coaxially, e.g. with a planetary step up gear, or at an offset from, and/or at an angle to the central drive shaft of the drive train 200.

When the truck 1 is in motion, as represented by FIG 1B, the stop-start controller 500 is arranged for performing a third and fourth step. In a third step, the stop-start controller 500 controls the drive train 200 to couple to the internal combustion engine 10, such that drive torque can be transmitted between the internal combustion engine 10 and the driven wheels 7 of the truck 1.

For example, to transmit drive torque from the internal combustion engine 10 to the driven wheels 7 of the truck 1, the coupling means 205 in the drive train 200 between the internal combustion engine 10 and the electric motor 210 can be controlled by the stop-start controller 500 to switch between an open, uncoupled position and a closed, coupled position, as shown in FIG 1B. In some embodiments, the stop start controller 500 is arranged for controlling the clutch to gradually move from an open position to a closed position, e.g. having one or multiple intermediate partially closed, slipping positions, to gradually transmit the drive torque from the internal combustion engine 10 to the driven wheels 7 of the truck

1. These coupling mechanisms in principle do not require the transmission in a neutral position. In other embodiments, by careful synchronization between electric engine and motor engine, non-slipping e.g. dog clutch type can be used.

In the fourth step, the stop-start controller 500 controls the electric motor 210 to provide the additional drive torque Td to the internal combustion engine 10, in order to crank the internal combustion engine 10.

The additional drive torque Td can for example be provided by the electric motor 210 to drive the drive train 200, which has previously been coupled to the internal combustion engine 10 in the third step, to crank the internal combustion engine in the fourth step. Since the truck 1 is in motion, the momentum of the truck provides a rolling torque on the driven wheels 7, which when coupled to the drive train can be used to at least partially crank the internal combustion engine

10. The stop-start controller 500 can control the electric motor 210, e.g. to compensate for the de-rate on propulsion power, which would occur when the engine 10 is cranked by momentum of the truck 1 only, because of the large displacement volume of the internal combustion engine.

Alternatively, the stop-start controller 500 can control the electric motor 210 to provide an additional drive torque Td which is sufficient to crank the internal combustion engine 10 without using the momentum of the truck 10, e.g. when the driven wheels 7 are decoupled from the drive train 200, e.g. by putting transmission 230 in neutral. A potential benefit of this arrangement is, that the forward momentum of the truck 1 is not affected by a de-rate on propulsion power caused by cranking the internal combustion engine 10.

In some embodiments, the requested launch torque is additionally based on a gross combination weight of the truck 1. The gross combination weight of the truck 1 can influence the effective magnitude of the required launch torque, e.g. a heavier loaded truck 1 may require a higher launch torque. The measured signals from the throttle pedal 80 of the truck 1 can be corrected with a value or offset based on the gross combination weight of the truck 1 to compensate for this effect. The gross combination weight value can be derived from sensors on board of the vehicle, e.g. from an electronic brake system or transmission system of the truck 1, or can be derived from lookup tables and external measurement equipment, e.g. a weighing platform, and uploaded or manually entered to the truck 1.

In other or further embodiments, the requested launch torque is additionally based on a road slope estimation. The measured signal from the throttle pedal 80 can be corrected with an offset representative of the estimated road slope. For example, a higher torque may be required to launch the truck 1 from an inclined road surface compared to when the truck is launched from a level road surface. Conversely, a lower torque may be required to launch the truck 1 from a declined road surface. The difference in torque can be based on an estimated actual road slope, e.g. by using an inclination sensor, gyroscope, accelerometer,

magnetometer, or inertial measurement unit, or based on one or multiple historic values of a road slope, e.g. from previous measurements or from a shared database. FIGs 2A-B show the truck 1 according to a further embodiment in which the drive train 200 comprises a clutch 220, arranged between the internal combustion engine and the electric motor 210. The stop-start controller 500 is arranged for controlling the clutch 220 to decouple the drive train 200 from the internal combustion engine 10 in the first step, as shown in FIG 2A, and to couple the drive train to the internal combustion engine in the third step, as shown in FIG 2B.

10 Preferably, the clutch 220 is of a type and specification that permits transmission of drive torque between the internal combustion engine 10 and the driven wheels 7 of the truck 1, as well as transmission of additional drive torque between the internal combustion engine 10 and the electric motor 210. Various types of clutch can be suitable for this purpose, e.g. friction clutches (wet/dry, single/multi-plate), centrifugal clutches, hydraulic clutches, dog clutches, electromagnetic clutches, diaphragm clutches, ete.

As is common for conventional trucks, the drive train 200 may optionally comprise a transmission 230 between the electric motor 210 and the driven wheels 7, as shown in FIG 2A and 2B. However, this is not an essential feature of the embodiment shown.

In some embodiments, the stop-start controller 500 is further arranged for controlling the electric motor 210 to reduce a rotational speed difference between the electric motor 210 and the internal combustion engine 10, prior to controlling the drive train 200 to couple to the internal combustion engine 10 in the third step.

For example, after the second step, when the truck 1 is launched to motion by the electric motor 210 while the internal combustion engine 10 is switched off, there can be a significant rotational speed difference between the electric motor 210 and the internal combustion engine 10. In the third step, when the internal combustion engine 10 is coupled to the drive train, the rotational speeds of the internal combustion engine 10 and the electric motor are preferably synchronized, e.g. by dissipation of energy by means of a clutch.

The stop-start controller 500 can e.g. be arranged for controlling the electric motor 210 prior to the third step, preferably while stop-start controller 500 controls the transmission 230 in neutral gear position, to reduce the rotational speed of the electric motor to at least approach the rotational speed of the internal combustion engine to reduce the dissipation of energy by the clutch, e.g. a rotational speed reduction of the electric motor 210 of at least 25%, or between 25% and 75%, or up to 100%. This reduces the time required to synchronize the rotational speeds of the internal combustion engine 10 and the drive train 200 when said components are coupled to each other in the third step.

For this purpose, the stop-start controller 500 is in some embodiments arranged for using the electric motor 210 as an electric generator, to convert kinetic energy of the drive train 200 into electric energy.

In this way the rotational speed difference between the electric motor 210 and the internal combustion engine 10 can be reduced, while the energy removed from the drive train 200 can be recovered for later use.

Alternatively or additionally, the drive train 200 can e.g. comprise a flywheel and the stop-start controller 500 can be arranged for coupling the flywheel to the drive train 200 to transfer kinetic energy from the drive train 200 into the flywheel where it is stored for later use, while the rotational speed difference between the electric motor 210 and the internal combustion engine 10 is reduced.

With increased rotational inertia of the flywheel, i.e. increased energy storage capacity, the rotational speed difference can be decreased further and more rapidly.

In other or further embodiments, the rotational speed difference between the electric motor 210 and the internal combustion engine 10 is reduced by the stop-start controller 500 by controlling the electric motor 210 to provide the additional drive torque in a negative direction, opposite to a direction of the requested launch torque.

For example, while the rotor of the electric motor 210, which drives the drive train 200, is rotating in a positive direction, coils of the electric motor 210 can be commutated in reverse order to provide a torque in an opposite, negative direction to reduce the rotational speed of the electric motor 210, while the start-stop controller 500 is arranged for controlling the transmission 230 in neutral gear position, to avoid reducing the forward speed of the truck 1. By actively controlling the electric motor 210, e.g. while transmission 230 is in neutral, to provide a negative torque to brake the rotation of the drive train 200, including its own rotation, the rotational speed difference between the electric motor 210 and the internal combustion engine 10 can be reduced within a considerably short time, depending on the power of the electric motor 210 and the amount of energy to be reduced from the drive train 200.

FIG 3 shows another or further embodiment of the truck 1, having a drive train 200 which comprises a transmission 230. The transmission 230 is arranged between the electric motor 210 and the driven wheels 7 of the truck 1. The transmission 230 can e.g. be a manual or automatic transmission, comprising various gears which can be controlled to shift to a higher or lower gear, to drive the driven wheels 7 of the truck 1 with a higher or lower transmission ratio, respectively. During a gear shift, transfer of drive torque in the transmission 230 is temporarily interrupted to allow (re)synchronization of gear pairs.

Beneficially, during a gear shift while drive torque is interrupted between the transmission 230 and the driven wheels 7 of the truck 1, the stop-start controller 500 can be arranged for controlling the drive train 200 to couple to the internal combustion engine 10, and controlling the electric motor 210 to crank the internal combustion engine 10. A potential advantage of this, is that the forward momentum of the truck 1, after being launched from standstill to motion by the electric motor 210 in the second step, is not decreased by the increase of inertia caused by the coupling of the internal combustion engine 10 to the drive train 200.

For example, to couple the drive train 200 to the internal combustion engine 10, the drive train 200 may comprise a coupling means 205 such as a clutch or a transmission arranged between the internal combustion engine 10 and the electric motor 210, as shown in FIG 3.

In some embodiments, the stop-start controller 500 is arranged for controlling the transmission 230 to launch the truck 1 from standstill to motion in a selected gear of the transmission 230, e.g. in a lower gear which is conventionally only used when the truck 1 is heavily loaded or launched from an inclined road surface. However, when using an electric motor 210 having a small size and strength in relation to the internal combustion engine 10, yet having a higher maximum rotational speed (RPM), the lower gears, e.g. the first and second gear ratios, of the truck 1 can beneficially be used to increase the effective launch torque of the truck 1 when driven by the electric motor 210 only. Preferably, the gear of the transmission 230 selected by the stop-start controller 500 to launch the truck 1 is selected in dependence of a maximum additional drive torque that can be provided by the electric motor 210. Additionally, when the truck 1 is in motion and driven by the electric motor 210 only, the stop-start controller 500 can be arranged for controlling the transmission 230 to shift to a higher gear, e.g. a second, third or fourth gear, in dependence of a maximum rotational speed of the electric motor 210.

Alternatively or additionally, the stop-start controller 500 can be arranged for selecting the gear of the transmission 230 to launch the truck 1, and selecting the moment to crank the internal combustion engine 10 in dependence of one or multiple other inputs, e.g. how aggressively the throttle pedal 80 is pressed by the driver, the gross combination weight of the truck 1, the road slope, or engine calibration parameters. The truck 1 may also include a manual override button which a driver can press to force the stop-start controller 500 to remain in the second step, in which the truck is driven by the electric motor 210 only, e.g. when the driver enters a “Green zone” to satisfy local air quality legislation.

In other or further embodiments, after controlling the electric motor 210 to crank the internal combustion engine 10 in the fourth step, the stop-start controller 500 is arranged for synchronizing the internal combustion engine 10 with the transmission 230 during a gear shift. Preferably, the stop-start controller 500 is arranged for using the electric motor 210 as an electric generator to convert kinetic energy of the internal combustion engine 10 into electric energy, to match a rotational speed of the internal combustion engine 10 with a rotational speed of the transmission 230. The electric energy can for example be stored in a battery or other electric power source for later use.

By using the electric motor 210 as an electric generator to extract kinetic energy from the drive train 200, e.g. to slow down the internal combustion engine 10 or the transmission 230, the time needed to execute a gear shift is reduced. This can, in turn, reduce torque interruption on the truck 1 during a gear shift and may provide a sense of improved drivability to the driver of the truck 1.

In conventional trucks, braking devices which dissipate kinetic energy into waste heat are typically used to reduce the rotational speed of the internal combustion engine 10 or the transmission 230 before gear synchronization.

Braking devices include e.g. mechanical friction elements. Alternatively, the rotational speed of the internal combustion engine 10 can e.g. be reduced by an endurance brake, which similarly dissipates kinetic energy into waste heat.

Instead, the electric motor 210 can be used as a generator to convert the kinetic energy into electric energy, which can be stored for later use. This may improve the total energy efficiency of the truck 1.

FIG 4 illustrates another or further embodiment of the truck 1. Here, after controlling the electric motor 210 to crank the internal combustion engine 10 in the fourth step, e.g. when the truck 1 is in motion and driven by the internal combustion engine 10, the stop-start controller 500 is arranged for providing a power boost to the truck 1. During a power hoost, the stop-start controller 500 controls the electric motor 210 and the internal combustion engine 10 to simultaneously drive the wheels 7 of the truck 1.

Compared to a conventional truck, which is launched by an internal combustion engine, the present invention proposes to launch the truck 1 from standstill to motion by using an electric motor 210, which may have a relatively low maximum torque compared to the maximum torque of the internal combustion engine 10. To compensate for a potential slower acceleration during the launch of the truck 1, the electric motor 210 can be employed to provide an additional power boost in a later phase, when the truck 1 is being driven by the internal combustion engine 10. Preferably, the power boost provided by the electric motor 210 is less than 40%, more preferably in the range of 10-25%, of the power of the internal combustion engine 10.

Preferably, the power boost is performed in dependence of a trigger signal 85, which can be manually activated such as by pressing a button on the steering wheel or dashboard of the truck 1, or (semi)automatically activated, e.g. having a controller activate the trigger signal based on sensor information.

In some embodiments, the throttle pedal 80 comprises a kick-down sensor to provide the trigger signal 85. For example, when the driver firmly and fully presses the throttle pedal 80, the trigger signal 85 is activated.

FIG 5 illustrates yet another or further embodiment of the truck 1, in which the truck 1 further comprises a radar sensor 90 for measuring a speed and distance of a predecessor vehicle, e.g. when driving in intermittent or slow driving traffic situation such as in a traffic jam. The stop-start controller 500 is arranged for controlling the drive train 200 to couple to the internal combustion engine 10 in the third step and controlling the electric motor 210 to crank the internal combustion engine 10 in the fourth step in dependence of measurements from said radar sensor

90. By having a stop-start controller 500 arranged for launching the truck 1 and cranking the internal combustion engine 10 in dependence of a speed and distance of a predecessor vehicle, the truck 1 can be controlled to automatically start driving and following the predecessor vehicle e.g. in a traffic jam situation. Engine stop- start can be an important fuel saving feature in these situations, because the truck 1 may often come to a standstill and be required to launch to motion again. By having a stop-start controller 500 arranged to take care of traffic jam situations, the stop-start controller 500 can optimize the off-time of the internal combustion engine 10, e.g. based on the speed and distance of a predecessor vehicle as measured by radar sensor 90. For example, by receiving information from the radar sensor 90 the stop- start controller 500 can derive that the predecessor vehicle is coming from motion to a standstill, and the stop-start controller 500 may control the internal combustion engine 10 to initiate an early shutdown for fuel saving purposes. As another example, by receiving information from the radar sensor 90 the stop-start controller 500 can derive that the predecessor vehicle is launched from standstill to motion, and the stop-start controller 500 may control the drive train 200 to decouple from the internal combustion engine 10, and control the electric motor 210 to launch the truck 1 to motion without cranking the internal combustion engine 10. Next, based on information from the radar sensor the stop-start controller 500 can decide to control the drive train 200 to couple to the internal combustion engine 10, and control the electric motor 210 to crank the internal combustion engine 10.

For example, if the predecessor vehicle was launched to motion and is driving at a steady pace, or keeps accelerating, the stop-start controller 500 can decide to control the drive train 200 to couple to the internal combustion engine 10, and control the electric motor 210 to crank the internal combustion engine 10, so that the power of the internal combustion engine 10 becomes available to drive the truck 1.

However, if for example the predecessor vehicle was launched to motion but is decelerating again, or is driving at a slow and steady pace, the stop-start controller 500 can decide to contro] the drive train 200 to remain uncoupled from the internal combustion engine 10, and control the electric motor 210 to provide the additional drive torque to the driven wheels 7 of the truck 1, so that the internal combustion engine 10 remains switched off to save fuel and/or to improve drivability.

FIG 6 provides an example of a functional architecture of a stop-start controller 500 of the truck 1. The stop-start controller may comprise a functional element, the Vehicle Control Unit (VCU) that performs the vehicle mode selection, and another element, the Transmission Control Unit (TCU) that performs the clutch control and the gear shift strategy. Other, alternative functional architectures can be envisaged by the person skilled in the art.

The stop-start controller 500 can for example receive a throttle position input from a throttle pedal, to define a requested launch torque. Alternatively or additionally, the stop-start controller 500 can receive a gross combination weight value and/or a road slope value from a vehicle mass estimation and a slope estimation, respectively.

The vehicle mass estimation can for example be derived from sensors on board of the vehicle, such as an electronic brake system or transmission system of the truck 10, or can be derived from lookup tables and external measurement equipment, e.g. a weighing platform, and uploaded or manually entered to the truck 10.

The slope estimation can for example be derived from an inclination sensor, gyroscope, accelerometer, magnetometer, or inertial measurement unit, or based on one or multiple historic values of a road slope, e.g. from previous measurements or from a shared database.

The Vehicle Control Unit (VCU) of the stop-start controller 500 can e.g. be arranged for controlling an electric motor (E-motor), shown in FIG 6 by means of an optional Hybrid Control Unit (HCU). Preferably, the VCU is arranged for directly controlling the electric motor.

The Transmission Control Unit (TCU) can e.g. be arranged for controlling a clutch and for controlling the gears of a transmission.

FIG 7 provides an example of a sequence of steps performed by the stop-start controller 500, depicted in a table.

In a first step, when the truck 1 is in standstill and the internal combustion engine 10 is switched off, the stop-start controller 500 controls the clutch 220 to open, to decouple the drive train 200 from the internal combustion engine 10. As shown in FIG 7, during step 1 the power generated by the electric motor 210 may be equal to zero and, the stop-start controller 500 controls the transmission 230 to shift to a neutral gear “N” such that the drive train 200 is also decoupled from the driven wheels 7 of the truck 1. In step 2, while the internal combustion engine 10 is switched off, the stop-start controller 500 controls the transmission to shift to a low, e.g. first gear and controls the electric motor 210 to provide the requested launch torque to the driven wheels 7 of the truck, to launch the truck 1 from standstill to motion.

During this step, the stop-start controller 500 controls clutch 220 to remain in the open position, to keep the internal combustion engine 10 decoupled from the drive train 200. Optionally, in step 2a, the transmission is controlled to a neutral position (N), in order to decouple the drive train from the driven wheels 7. Next, in step 3, when the truck 1 is in motion, the stop-start controller 500 controls the clutch 220 to close, to couple the electric motor 210 to the internal combustion engine 10. While a preferred embodiment has the transmission switched to neutral, in some scenario’s this step is optional, e.g. when impulse of the driven wheels is used, e.g. in combination with a slipping clutch and assisted by the additional torque of the e-motor, to crank the ICE.

Alternatively, the electric motor is simply disengaged by switching the transmission to Neutral.

In that case the stop-start controller 500 controls the transmission to shift to a neutral gear

“N”, to decouple the drive train 200 from the driven wheels 7 of the truck 1, to avoid a decrease in forward momentum of the truck 1 caused by the coupling of the internal combustion engine 10 to the drive train 200. For example, the stop-start controller 500 can be arranged to control the clutch 220 to move to a closed, coupled position once the rotational speed difference between the electric motor 210 and internal combustion engine 10 is small enough.

In a step 4, while the truck 1 is in motion, the stop-start controller 500 controls the electric motor 210 to provide its torque to crank the internal combustion engine 10. The stop-start controller 500 controls the clutch 220 to remain in the closed position, to keep the internal combustion engine 10 coupled to the electric motor 210. The transmission 230 is preferably controlled by the stop-start controller 500 to stay in neutral gear “N” in which the drive train 200 is decoupled from the driven wheels 7. After the internal combustion engine 10 is cranked, the transmission 230 can be synchronized with the internal combustion engine 10, as shown in the step 5 of FIG 7. By using the electric motor 210 as a torque boost, to match a rotational speed of the internal combustion engine 10 with a rotational speed of the transmission 230, a faster gear shift can be achieved while the total energy efficiency of the truck 1 can be improved.

For example, after the truck 1 has been launched from standstill to motion by the electric motor 210 and the internal combustion engine 10 has been cranked, the stop-start controller 500 can control the transmission 230 to shift to a higher gear, such as a third gear, suitable for driving the truck 1 when powered by the internal combustion engine 10 only.

During a gear shift, the rotational speed difference between the internal combustion engine 10, which was previously switched off, and the transmission 230, which was previously driven in a low gear by the electric motor 210, is preferably limited, e.g. to reduce the time needed to perform the gear shift and to reduce dissipation of waste heat in friction couplings.

In step 6 of FIG 7, the stop-start controller 500 controls the electric motor 210 to stop providing drive torque to the driven wheels 7, and the truck 1 may be powered by the internal combustion engine 10 only.

As shown in step 7, the stop-start controller 500 may use the electric motor 210 as an electric generator for synchronizing the internal combustion engine 10 and the transmission 230 during gear shifts, to match the rotational speed of the internal combustion engine 10 with the rotational speed of the transmission 230, to enable fast shifts while recovering energy from the drive train 200. Synchronization may be provided by controlling the electric motor 210 to provide the additional drive torque Td in a negative direction, opposite to a direction of the requested launch torque, to thereby reduce the rotational speed difference between the electric motor and the internal combustion engine . In this way, the rotational speed of the internal combustion engine 10 can actively be matched by the rotational speed of the transmission 230, to achieve a faster gear shift while the total energy efficiency of the truck 1 is improved. This negative torque may be provided in ‘GEN’ mode, or even actively, by reversing the torque of the electric motor.

Additionally, in the sixth step the stop-start controller 500 can control the electric motor 210 to provide additional drive torque Td to the driven wheels 7 of the truck 1 while the truck 1 is driven by the internal combustion engine 10, to provide additional boost power, e.g. to compensate for the slower vehicle launch in step two because the electric motor 210 has limited torque capabilities compared to the internal combustion engine 10.

FIG 8 provides another example of a launch sequence of the truck 1 performed by the stop-start controller 500, depicted in a graph. The stop-start controller may receive a signal from a throttle pedal, e.g. a percentage of a maximum throttle position, representative of a requested launch torque, while the truck is in standstill and the internal combustion engine (ICE) is switched off.

At this point in time, the stop-start controller performs a first step of controlling the drive train to decouple from the internal combustion engine, e.g. by controlling the clutch to switch to an open state. In a second step, the stop-start controller controls the electric motor in the drive train to provide the requested additional drive torque, to launch the truck to motion without cranking the internal combustion engine regardless of the magnitude of the requested launch torque. As shown in FIG 8, the truck is driven by the electric motor only, in E- motor drive, in the first and second gear of the transmission, e.g. until the stop-

start controller identifies that the driver demand exceeds the maximum torque of the electric motor.

In some embodiments, as shown in FIG 8, the stop-start controller can be arranged to schedule controlling the drive train to couple to the internal combustion engine in the third step, by controlling the clutch to switch to a closed state, and controlling the electric motor to provide the additional drive torque to the internal combustion engine to crank the internal combustion engine in the fourth step, during a gear shift consecutive to the requested launch torque exceeding the maximum torque that can be provided on the driven wheels when the truck is driven by the electric motor only.

By performing the third and fourth step during a gear shift, while the transmission is in neutral and the drive train is decoupled from the driven wheels of the truck, the forward momentum of the truck is minimally reduced by the inertia added to the drive train when coupling and cranking the internal combustion engine. After the internal combustion engine has been cranked by the electric motor in the fourth step, the stop-start controller can be arranged for controlling the electric motor to stop providing drive torque such that the truck is powered by the internal combustion engine only, in ICE drive.

Claims

Conclusions

A truck powered by a propulsion, said propulsion comprising: — an internal combustion engine; — a powertrain extending from the internal combustion engine and adapted to transmit driving torque between the internal combustion engine and driving wheels of the truck, the powertrain comprising an electric motor providing additional driving torque between the internal combustion engine and driving wheels of the truck the truck; and - a stop-start controller adapted to control the powertrain to provide a demanded drive-away torque, based at least on measured signals from an accelerator pedal of the truck, for starting the truck from a standstill to move while the internal combustion engine is turned off 1s; wherein, while the truck is at a standstill, the stop-start controller is arranged to perform 1) in a first step, controlling the powertrain to decouple from the internal combustion engine; and 1) in a second step, controlling the electric motor in the drivetrain to provide the additional drive torque, to drive the truck off to motion without cranking the internal combustion engine, regardless of a magnitude of the starting torque demanded; wherein, when the truck is in motion, the stop-start controller is arranged to perform iii) in a third step, controlling the powertrain to couple to the internal combustion engine; and 1v) in a fourth step, controlling the electric motor to provide the additional driving torque to the internal combustion engine to crank the internal combustion engine.

A truck according to claim 1, wherein the drivetrain comprises a clutch arranged between the internal combustion engine and the electric motor for decoupling the drivetrain from the internal combustion engine in the first step, and coupling the drivetrain to the internal combustion engine. in the third step, and wherein the stop-start controller is arranged to control the clutch accordingly.

The truck of claim 2, wherein, prior to controlling the drivetrain to engage the internal combustion engine in the third step, the stop-start controller is arranged to control the electric motor to adjust a rotational speed difference between the electric motor and the electric motor. to downsize the internal combustion engine.

The truck of claim 3, wherein the stop-start controller is adapted to use the electric motor as an electric generator to convert kinetic energy of the drivetrain to electric energy to reduce the rotational speed difference between the electric motor and the internal combustion engine. .

A truck according to claim 3, wherein the stop-start controller is adapted to control the electric motor to provide the additional driving torque in a negative direction, opposite to a direction of the requested driving torque, to reduce the rotational speed difference between the electric motor and to downsize the internal combustion engine.

A truck according to any one of the preceding claims, wherein the drive train comprises a gearbox arranged between the electric motor and the drive wheels of the truck, the stop-start controller being arranged to control the drive train to be coupled to the internal combustion engine in the third step, and for controlling the electric motor to crank the internal combustion engine in the fourth step, during a shift moment while driving torque between the gearbox and the driving wheels of the truck is interrupted.

A truck according to claim 6, wherein the stop-start controller is adapted to control the gearbox to start the truck from standstill to movement in a selected gear of the gearbox, depending on a maximum additional driving torque that can be provided by the electric motor.

A truck according to claim 7, wherein the stop-start controller is adapted to control the gearbox to shift to a higher gear when the truck is in motion,

depending on a maximum rotational speed of the electric motor.

A truck according to any one of claims 6 to 8, wherein after controlling the electric motor to crank the internal combustion engine in the fourth step, the stop-start controller is arranged to synchronize the internal combustion engine with the gearbox during a switching moment, by using the electric motor as an electric generator to convert kinetic energy of the internal combustion engine into electrical energy, to match a rotational speed of the internal combustion engine with a rotational speed of the gearbox.

A truck according to any one of the preceding claims, wherein, after controlling the electric motor to crank the internal combustion engine in the fourth step, the stop-start controller is arranged to provide a power boost to the truck by controlling the electric motor and the internal combustion engine to simultaneously drive the wheels of the truck in response to a trigger signal.

The truck of claim 10, wherein the accelerator pedal includes a kickdown sensor to provide the trigger signal.

A truck according to any one of the preceding claims, wherein the required starting torque is additionally based on a lane slope estimate.

A truck according to any one of the preceding claims, wherein the required starting torque is additionally based on a gross combination weight of the truck.

A truck according to any one of the preceding claims, further comprising a radar sensor for measuring a speed and distance of a vehicle in front, wherein the stop-start controller is adapted to control the powertrain for coupling to the internal combustion engine in the third step and for controlling the electric motor to crank the internal combustion engine in the fourth step in dependence on measurements of said radar sensor.